This invention relates to envelope handling equipment and deals more particularly with such equipment for checking a plurality of envelopes for the presence of enclosed documents.
The device of this invention may be used in various different applications where it is necessary or desirable to inspect a large number of envelopes for the presence of enclosed documents and for segregating from the remainder of the envelopes those suspected, as a result of the inspection, of containing documents. For example, many businesses, government agencies, and other institutions have mail receiving or similar departments to which documents such as checks, bills, order forms, receipts and the like are delivered in sealed delivery or mailing envelopes. After receipt of the envelopes, they are opened and their contents extracted. After such extraction the envelopes are normally considered waste and are suitably disposed of. The envelope opening and content extracting processes may be carried out either by hand or through the use of automatic machinery; but, in either case, it is possible that some mistakes may be made causing some forwarded documents to be unextracted from their envelopes and to be accordingly consigned to waste with the envelopes and destroyed. The device of this invention is particularly useful in this situation for checking previously opened and supposedly emptied envelopes and for retrieving those suspected of containing enclosed documents prior to their destruction.
The device of the invention relies upon sensing the opacity of an envelope for determining the presence or absence of a document in an envelope passing an inspection station. The use of opacity sensors for detecting the presence of enclosed documents within envelopes has been known in the past, and basically involves the fact that the opacity of an envelope containing an enclosed document is greater than that of one not containing a document. However, problems in reliably detecting the presence of enclosed documents by opacity sensors are presented by the fact that the opacity of any given envelope itself varies over its body due to the presence of seams in the envelope where two or more portions of the envelope blank are overlaped and secured to one another by adhesive, and the fact that the opacities of the envelopes in any given group may vary widely from one envelope to another because of differences in the sheet materials from which the various envelopes are made.
The device of this invention overcomes these problems and provides reliable document detection by compensating for opacity differences due to seams and for opacity differences in the sheet materials from which individual envelopes are made.
Other objects and advantages of the invention will be apparent from the following description and from the drawings forming a part hereof.